Patent GB-214195-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1923-11-05
Abstract: 214,195. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Ostline, J. E.). April 9, 1923, [Convention date]. Tell-tale apparatus.-Arrangements at a manual telephone exchange for indicating to the operator the number of a wanted line, the digits of the number having been transmitted from a distant automatic exchange by means of code combinations, comprise a set of storage relays SR .. SR<3>, Fig. 6, in addition to a set of indicating relays SRS .. SRS<3>, Fig. 7, the number being first set up on the storage relays and then transferred to the indicator relays so that the storage relays may be storing a second number whilst the first number is still displayed on the indicator lamps. The code combinations employed are obtained by connecting a variable potential to one wire of the inter-exchange. trunk, whilst at the same time transmitting over the other wire a varying number of impulses, in no case exceeding three per digit, the codes for the various digits being shown in Fig. 10. Decoding of impulses and setting of register relays SR .. SR<3>, Fig. 6. Whilst the coded digits are being transmitted the trunk conductor which carries the variable potential (the " control conductor ") is connected over lead 430 to relays 512, 513, whilst the " pulsing conductor " is connected to relay 514. Relay 511 also is operated. For digits 1-3 and 0 in which the control conductor is disconnected, relays 512, 513 remain de-energized; for digits 4-6, relay 512 alone energizes in series with a high resistance; whilst for digits 7-9, relays 512, 513 both energize. At each impulse over the pulsing conductor, relay 514 energizes and operates one of the relays SR &c., the particular one operated depending upon the condition of relays 512, 513. Each of the relays SR &c. is of the type which, when first operated over its left-hand winding closes only its right-hand armature, thus preparing a locking-circuit which however is temporarily short-circuited. At the end of the operating impulse, the relay is locked to conductor 525 and operates also its left-hand armatures. A " change-over " impulse, comprising a direct ground connection to the control conductor energizes relay 512 (if not already energized which it would be if the preceding digit were 4 .. 9) so that relay 533 (or 548, 569, 572) is partially energized over its left-hand winding. A succeeding break in this direct ground connection causes the full operation of relay 533 which transfers the operating conductors from one set of register relays to the next. In the example under consideration, for the first digit 2, relays 512, 513 are de-energized and the two impulses through relay 514 operate relays 521, 529 respectively. The succeeding " chance-over " impulse causes the complete operation of relay 533 so that the second digit 4, for which relay 512 is energized, causes the operation of relay 538. In a similar manner the third digit 9 operates relays 553, 559, 564, whilst for the fourth digit 0, no impulses are transmitted and no relays SR<3> are energized. The final " change-over " impulse operates relay 572. Transfer of wanted number from register relays SR - - SR<3> to indicator relays SRS - - SRS<3>, Fig. 7. Relay 572 completes a ground connection from armature 574 to conductor 526 which causes the partial operation of indicator relays 611, 612, 613, 614, 615, 616 to prepare locking-circuits to conductor 578. Relay 540 energizes, operates relay 541 and removes ground from conductor 526 so that the partially-operated indicator relays 611 .. 616 are enabled to operate completely over their locking circuits. The grounding of lead 579 at armature 581 causes the lighting of the selected lamps 2, 4, 9, 0 in the four groups respectively. Relay 511, 512 .. 514 are now disconnected, relay 511 unlocking all the operated relays of theregister set SR .. SR<3>. A second wanted number may now be recorded on this set of relays. Release of lamp indicator. When the connection has been completed, relay 540 de-energizes, opening the circuit of relay 541 which by its slow release permits a momentary current through relay 542. Relay 542 is provided to ensure the opening of lead 578 to release the indicator relays 611 .. 616 in case contacts 524 should be closed owing to the operation of relay 511 for a second call.